B350 1 Ton Van V8-5.9L VIN Z (1992)
Brake Switch (Cruise Control): Description and Operation
Vehicles equipped with speed control have a brake switch that controls three separate circuits. One circuit controls the power to the brake lights; the
other two circuits relate to the speed control system as follows:
Servo valve power circuit: - Power for the servo comes from the ON/OFF switch and goes through the brake switch to the servo. The switch
circuit is normally closed when the brake is not depressed. Either depressing the brake or turning the ON/OFF switch off will open the circuit and
cut all power to the servo.
Brake switch sense: - A wire from the ON/OFF switch is connected to cavity no. 29 of the engine controller 6O-way connector. This wire is what
the controller uses to indicate the ON/OFF status.